Understanding the impact of living in poverty on children's development is as important as ever, given that the child poverty rate in the U.S. has remained stable at 18 percent for the last several years (National Center for Children in Poverty, 2006) and is the second highest in the industrialized world (only slightly less than Mexico: UNICEF, 2005). Recent advances in research on socioeconomic disadvantage and child development by our research team and others have shifted concern from whether income poverty has an impact on children's outcomes to more complex questions regarding how poverty takes a toll on children, questions of greater relevance to the design of program and policy innovations. Thus our objective in this current proposal is to strengthen the field's understanding of the mechanisms through which families'trajectories of income and hardship affect children's trajectories of success versus difficulty in academic and socio-emotional domains. In addition, we propose to expand our empirical lens beyond families to the important contribution of school socio-economic disadvantage to children's development. In what represents a synthesis of the investigators'expertise in developmental psychology, social work, education, public policy, and sociology, we propose to address the following aims: Aim I: To examine how the timing, sequence, and duration of changes in family- level disadvantage impact the development of children's academic skills and social-emotional competence across elementary school and into middle school. Aim II: To apply the theoretical frame of specificity of environmental action to understanding the impact of school-level disadvantage on children's academic achievement and social-emotional competence. Aim III: To examine the independent, joint and sequential dynamic impacts of family-level and school-level contextual transitions on families'income and hardship and in turn on the development of children's achievement and social-emotional competence. We will analyze data from all five waves of the Early Childhood Longitudinal Study, Kindergarten Class of 1998-99 (ECLS-K) to address these aims. Findings from this research have the potential to contribute to policy and program advances that will enhance the life chances of children in poor and low income families. This project aims to understand the mechanisms through which family-level and school-level poverty and disadvantage affect children's cognitive and social-emotional development from kindergarten through 8th grade. Findings from this research have the potential to contribute to policy and program advances that will enhance the life chances of children in poor and low income families.